(a) Field of the Invention
The present invention relates to a hybrid electric vehicle, and more particularly, to a method and an apparatus for controlling engine start for a hybrid electric vehicle.
(b) Description of the Related Art
As is generally known in the art, a hybrid electric vehicle uses an internal combustion engine and a battery power source together. Particularly, the hybrid electric vehicle efficiently combines the torque from the internal combustion engine and torque from the motor. In general, a hybrid electric vehicle includes an engine, a motor, an engine clutch that selectively connects the engine to the motor, a transmission, a differential gear device, a battery, a hybrid starter & generator (HSG) configured to start the engine or generate power based on output of the engine, and a plurality of wheels. The HSG may refer to an integrated starter & generator (ISG).
Additionally, a hybrid electric vehicle enables driving in an electric vehicle (EV) mode, in which torque of the motor is used; a hybrid electric vehicle (HEV) mode, in which torque of the engine is used as main torque and torque of the motor is used as auxiliary torque; and a regenerative braking mode, in which braking and inertial energy are recovered through electrical power generation of the motor while braking of the vehicle or while driving of the vehicle by inertia to be charged in the battery. The EV mode and the HEV mode are enabled by engaging or releasing the engine clutch based on a manipulation (e.g., engagement) of an accelerator pedal or brake pedal by a driver, a vehicle speed, a state of charge (SOC) of the battery, and the like.
By using both mechanical energy of the engine and electrical energy of the battery, using optimal operation regions of the engine and the motor, and recovering the energy upon braking, fuel efficiency in a hybrid electric vehicle may be improved and the energy of the hybrid electric vehicle may be efficiently used.
When the hybrid electric vehicle starts from a stopped state, the hybrid electric vehicle generally runs using electrical energy of the battery. At the time of starting (e.g., launching from a stopped state), the hybrid electric vehicle may determine whether to start the engine in consideration of energy efficiency of the engine and energy efficiency of the motor. For example, the engine may be started when a demand power of a driver is greater than a predetermined power. The engine of the hybrid electric vehicle may be frequently started and stopped in a specific traveling status (e.g., a congested road and a parking lot) based on the demand power of the driver. Accordingly, energy efficiency of the hybrid electric vehicle may be deteriorated due to unnecessary fuel consumption.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.